High storage capacities of up to 7% by weight of hydrogen, relative to the mass of the alloy, are obtained with magnesium and magnesium/nickel alloys. To expel the hydrogen, however, temperatures of more than 250.degree. C. are required, with a large supply of energy at the same time. The high temperature level and the high energy requirement for expelling the hydrogen have the effect that, for example, a motor vehicle with an internal combustion engine, cannot exclusively be operated from these stores. This occurs because the energy contained in the exhaust gas, in the most favorable case (full load), is sufficient for meeting 50% of the hydrogen requirement of the internal combustion engine from a magnesium or magnesium/nickel store. Thus, the remaining hydrogen demand must be taken from a hydride store. For example, this store can be titanium/iron hydride (a typical low-temperature hydride store) which can be operated at temperatures down to below 0.degree. C. These low-temperature hydride stores have the disadvantage of only having a low hydrogen storage capacity.
Storage materials have been developed in the past, which have a relatively high storage capacity but from which hydrogen is nevertheless expelled at temperatures of up to about 250.degree. C. U.S. Pat. No. 4,160,014 describes a hydrogen storage material of the formula Ti.sub.1-x Zr.sub.x Mn.sub.2-y-z Cr.sub.y V.sub.z, wherein x=0.05 to 0.4, y=0 to 1 and z=0 to 0.4. Up to about 2% by weight of hydrogen can be stored in such an alloy. In addition to this relatively low storage capacity, these alloys also have the disadvantage that the price of the alloy is very high when metallic vanadium is used.
Moreover, U.S. Pat. No. 4,111,689 has disclosed a storage alloy which comprises 31 to 46% by weight of titanium, 5 to 33% by weight of vanadium and 36 to 53% by weight of iron and/or manganese. Although alloys of this type have a greater storage capacity for hydrogen than the alloy according to U.S. Pat. No. 4,160,014, hereby incorporated by reference, they have the disadvantage that temperatures of at least 250.degree. C. are necessary in order to completely expel the hydrogen. At temperatures of up to about 100.degree. C., about 80% of the hydrogen content can be discharged in the best case. However, a high discharge capacity, particularly at low temperatures, is frequently necessary in industry because the heat required for liberating the hydrogen from the hydride stores is often available only at a low temperature level.
It is, therefore, the object of the present invention to disclose a hydrogen storage material which has a large storage capacity for hydrogen and from which at least 90% of the hydrogen content is liberated under a pressure of one bar at a temperature of up to 100.degree. C.
These and other objects, features and advantages of the present invention will become more apparent from the following description which shows, for purposes of illustration only, embodiments of the present invention.